Analyses of primary structures of hemoglobins from representative nonhuman primates will be conducted with the intention of reconstructing the course of evolutionary divergence of beta- from gamma-chain genes that occurred during the period following establishment of the anthropoid lineage. In addition, it is likely that such studies will provide insight into the nature of the advantages gained by relegation of gamma-chain synthesis to the fetal stage of the life cycle as well as into the origins of the multiple gamma-chain loci of man and other members of the Anthropoidea. Studies on the induction of fetal hemoglobin synthesis in adult monkeys will also be conducted. Changes in levels of hemoglobin F and HbF-containing cells will be monitored by alkali denaturation and the application of fluorescent anti-HbF antibodies to blood smears. Animals will be followed throughout the course of anemic episodes produced by phlebotomy and administration of phenylhydrazine, and it is anticipated that the results of these studies will provide insight into the process of differentiation of erythroid cells, as well as into aspects of the gamma yields beta switch that occurs during the normal course of ontogenesis.